Embryonic diapause mink uterus

Mammalian embryonic diapause is a reproductive phenomenon defined by the reversible arrest in blastocyst development and metabolic activity within the uterus which synchronously becomes quiescent to implantation. This natural strategy, evident in over 130 species across eight orders, can temporally uncouple conception from delivery until conditions are favorable for the survival of the mother and newborn. While the maternal endocrine milieu has been shown to be important for this process, the local molecular mechanisms by which the uterus and embryo achieve quiescence, maintain blastocyst survival and then resumes blastocyst activation with subsequent implantation in response to endocrine cues remains unclear...

The reproduction of the mink, Neovison vison, has been extensively studied over the past 70 years. The endocrine control of pregnancy is reasonably well understood, but our understanding of early embryo development is limited. The mink is one of the best characterized mammals for the study of embryonic diapause, but in order to unravel the complex interactions that occur between the blastocyst and the uterus during diapause and reactivation, a defined culture media system that supports growth is essential...

Embryonic diapause is an evolutionary strategy to ensure that offspring are born when maternal and environmental conditions are optimal for survival. In many species of carnivores, obligate embryonic diapause occurs in every gestation. In mustelids, the regulation of diapause and reactivation is influenced by photoperiod, which then acts to regulate the secretion of pituitary prolactin. Prolactin in turn regulates ovarian steroid function. Reciprocal embryo transplant studies indicate that this state of embryonic arrest is conferred by uterine conditions and is presumed to be due to a lack of specific factors necessary for continued development...

Embryonic diapause is an evolutionary strategy to ensure that offspring are born when maternal and environmental conditions are optimal for survival. In many species of carnivores, obligate embryonic diapause occurs in every gestation. Reciprocal embryo transplant studies indicate that embryo arrest during diapause is conferred by uterine conditions and is due to a lack of specific factors necessary for continued development. In previous studies, global gene expression analysis revealed reduced uterine expression during diapause of a cluster of genes in the mink that regulate the abundance of polyamines, including ornithine decarboxylase 1 (ODC1)...

The marsupial tammar wallaby has the longest period of embryonic diapause of any mammal. Reproduction in the tammar is seasonal, regulated by photoperiod and also lactation. Reactivation is triggered by falling daylength after the austral summer solstice in December. Young are born late January and commence a 9-10-month lactation. Females mate immediately after birth. The resulting conceptus develops over 6- 7 days to form a unilaminar blastocyst of 80-100 cells and enters lactationally, and later seasonally, controlled diapause...

Mammalian embryonic diapause is a phenomenon defined by the temporary arrest in blastocyst growth and metabolic activity within the uterus which synchronously becomes quiescent to blastocyst activation and implantation. This reproductive strategy temporally uncouples conception from parturition until environmental or maternal conditions are favourable for the survival of the mother and newborn. The underlying molecular mechanism by which the uterus and embryo temporarily achieve quiescence, maintain blastocyst survival and then resume blastocyst activation with subsequent implantation remains unknown...

Embryonic diapause is an evolutionary strategy by which a reversible arrest in embryo development occurs. In its two forms, facultative and obligate, it assures that offspring are born when optimal maternal and environmental conditions are present to ensure maximal survival. We have explored obligate delayed implantation in the mink (Neovison vison) over four decades: first by evaluation of the environmental regulation, then by determination of the pituitary factors that maintain diapause and provoke implantation followed by exploration of the ovarian contribution to the process...

Embryonic diapause is the reversible arrest of embryo development prior to implantation under a regime of uterine control that is not well understood. Our objective was to explore uterine modifications associated with the emergence of embryonic diapause in the mink, a species in which embryonic diapause characterizes every gestation. We investigated the uterine transcriptome at reactivation using the suppressive subtractive hybridization technique. A library of 123 differentially expressed genes between uteri with blastocysts in diapause and reactivated blastocysts was generated...

Embryonic diapause is a poorly understood phenomenon of reversible arrest of embryo development prior to implantation. In many carnivores, such as the mink (Neovison vison), obligate diapause characterizes each gestation. Embryo reactivation is controlled by the uterus by mechanisms that remain elusive. Because polyamines are essential regulators of cell proliferation and growth, it was hypothesized that they trigger embryo reactivation. To test this, mated mink females were treated with α-difluoromethylornithine, an inhibitor of ornithine decarboxylase 1, the rate-limiting enzyme in polyamine biosynthesis, or saline as a control during the first 5 d of reactivation...

Superfetation is understood as another conception during an already ongoing pregnancy. This implies the existence of young of different developmental stages within the female reproductive tract during certain periods of pregnancy. Nevertheless, a clear definition of the term as well as distinct criteria to identify the occurrence of superfetation in a species is missing. The variable anatomy of mammalian reproductive tracts seems to make the occurrence of superfetation more or less likely but impedes the simple evaluation of whether it is present or not...

Vascular endothelial growth factor (VEGF) is an essential angiogenic signaling element that acts through its two tyrosine kinase receptors, inducing both proliferation of endothelial cells and vascular permeability. Given the importance of vasculogenesis and angiogenesis to early pregnancy, it is of interest to understand the mechanisms regulating vascular development at this stage. We previously demonstrated that VEGF and receptors are up-regulated during embryo implantation in an unique animal model, the mink, a species displaying obligate embryonic diapause...

Expression of vascular endothelial growth factor (VEGF) isoforms and its receptors, Flt-1 and KDR, was investigated during the period of peri-implantation in mink, a species that displays obligate embryonic diapause. Uterine samples were collected during diapause, embryo activation, and implantation from pseudopregnant and anestrous animals and analyzed by semiquantitative reverse transcription polymerase chain reaction and immunohistochemistry. The abundance of mRNA of VEGF isoforms 120, 164, and 188 was highest during late embryo activation and at implantation...

Leukemia inhibitory factor (LIF) is essential for embryo implantation in mice. Whether LIF plays a role in termination of embryonic diapause and initiation of implantation in carnivores, especially in species with obligate delayed implantation such as the mink, is not known. The objectives of this study were to clone the LIF coding sequence in the mink and determine its mRNA abundance in the uterus through embryonic diapause, implantation, and early postimplantation. We show that the mink LIF cDNA contains 609 nt encoding a deduced protein of 203 amino acids...

Experiments were carried out to investigate the abundance of mRNA for luteotrophic receptors and steroidogenic elements in the ovaries and corpora lutea of mink during the embryonic diapause, peri-implantation and postimplantation pregnancy. The second aim was to determine whether the mink placenta synthesized progesterone. Homologous cDNA probes for the mink LH and prolactin receptors were generated by the polymerase chain reaction. Heterologous cDNA probes for steroidogenic acute regulatory protein (StAR), cytochrome P450 side chain cleavage (P450scc) and 3 beta-hydroxysteroid dehydrogenase-delta 4-delta 5 isomerase (3 beta HSD) were also used...

Embryonic diapause occurs in many species of vertebrates, but the physiological mechanisms which control this fascinating process are exceedingly different in the diverse groups which employ this reproductive strategy. In nonmammalian species and some bats, reduction in rate of embryonic development is temperature dependent, but this is not the case in most mammals. Development becomes arrested at the blastocyst stage of embryogenesis in mammals which exhibit delayed implantation, whereas postimplantation development is continuous but retarded in species exhibiting delayed development...

Mink endometrial cell lines were established by stable transfection of a plasmid vector encoding the SV40 large T antigen driven by the human beta-actin promoter. A second plasmid vector, pSV2neo, was employed for selection of transfected cells. Specificity and homogeneity of consequent cell lines were evaluated by immunocytochemistry employing antibodies against cytokeratin, desmin, and vimentin. Cytokeratin was found exclusively in epithelial cells, whereas vimentin appeared primarily in stromal cells. Neither cell line showed detectable desmin activity...

Adult and pubertal female mink mated on 4 March were administered 2.5 mg medroxyprogesterone acetate (MPA) or control vehicle on 9-11 March. Pregnancies were shorter (P less than 0.01) in adult (60 +/- 2 days) than in pubertal (72 +/- 0.7 days) control animals. Treatment with MPA reduced (P less than 0.01) the length of pregnancy in both adult (51 +/- 1 days) and pubertal (60 +/- 2 days) mink but did not significantly affect serum progesterone levels on 3-4 April. Observations at laparotomy during April confirmed the effects of age and treatment on the time of implantation and suggested that implantation sites become grossly visible 28 days before parturition...

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Experiments were conducted to determine if prolactin receptors were present in the mink ovary, and to examine the relationship between receptor numbers and serum levels of prolactin (PRL) during embryonic diapause and blastocyst reactivation. For analysis of the physicochemical properties of prolactin receptors, ovaries were obtained from anestrous mink. All binding determinations were made using 125I-ovine prolactin (125I-oPRL), and 20 micrograms of tissue protein from the 100,000 X g particulate fraction...